The most widely used anionic surfactants in cleansing compositions are alkyl sulphates, polyoxyethylene alkyl sulphates and alkyl benzene sulphonates. These compounds are known to have a good foaming and deterging power. Due to their harshness, however, they are not desirable as components for cleansing compositions topically applied to human skin and hair. Their damaging effect particularly where young, tender or damaged skin is involved, has been the subject of intense study for many years.
On the other hand milder surfactants often suffer from the draw-back that they do not provide high foam which is very important for the consumer. Therefore, there is a strong need for products which are not only very mild but also possess an excellent foaming power.
U.S. Pat. No. 3,728,447 (C. J. Patterson) discloses hair shampoo compositions containing fatty acid lactylates or glycolates. While the cleaning action of shampoos based on the fatty acid lactylates is satisfactory the foam is minimal. In order to achieve higher foaming action it is described to include harsh detergents such as sodium lauryl sulphate or triethanolamine lauryl sulphate. When the lactylates are used in conjunction with such a booster detergent the quantity of the lactylates present in the composition is reduced down to about 1 to 2% by weight.
EP-A-224 796 (Kao) describes a detergent composition comprising (a) a phosphate surfactant and (b) an acyl lactylate having an acyl group containing 12 to 18 carbons atoms. The detergent composition is said to have excellent foaming characteristics as well as excellent detergency and mildness to the skin and hair. It is taught that these characteristics are only achievable if the acyl lactylate is used in an amount of not more than 5% by weight and preferably not more than 3% by weight of the composition.
U.S. Pat. No. 4,761,279 (Eastman Kodak) describes shaving cream formulations comprising salts of acyl lactylates, saturated monoglycerides, propyleneglycol mono esters and humectants.
U.S. Pat. No. 4,946,832 (RITA Corporation) describes cosmetic base compositions comprising 1 to 15% by weight sucrose fatty acid ester, 3 to 45% by weight acyl lactylate or its alkali metal salts and solvent. The compositions promote wound healing and reduces skin dryness. Foaming properties of the compositions are not reported.
Applicants in their search for mild cleansing compositions, in particular for cleansing human skin or hair, with the added attribute that full lather is produced, have unexpectedly discovered that a narrow range of acyl lactylates in combination with specific co-surfactants provide the desired effects when used in particular amounts. The compositions so obtained are capable of producing a superior lather and accordingly have great consumer appeal. Also, the compositions are so mild that they can safely be used for cleansing the skin and the hair and other more delicate skin areas.